Journal of Lipid Research, Vol 24, 1049-1059, Copyright © 1983 by Lipid Research, Inc.

ARTICLES

Regulation of acyl CoA:cholesterol acyltransferase by 25- hydroxycholesterol in rabbit intestinal microsomes and absorptive cells

FJ Field and SN Mathur

The regulation of rabbit intestinal acyl CoA:cholesterol acyltransferase (ACAT) by 25-hydroxycholesterol was studied. 25- Hydroxycholesterol significantly increased jejunal microsomal ACAT activity. The stimulation of ACAT activity by 25-hydroxycholesterol was inversely related to microsomal cholesterol content. In enterocytes, 25- hydroxycholesterol stimulated cholesteryl ester synthesis 6-fold. The esterification of cholesterol, taken up by enterocytes from liposomes or bile salt micelles, was increased by 25-hydroxycholesterol. This, however, did not affect the rate of uptake of cholesterol by the cells. In intestinal cells from rabbits fed cholesterol, the effect of 25- hydroxycholesterol on cholesteryl ester synthesis was 50% of that in cells prepared from animals fed no cholesterol. 25-Hydroxycholesterol stimulated the esterification of newly synthesized cholesterol. As new free cholesterol increased in enterocytes, 25-hydroxycholesterol lost its effect. Despite large amounts of newly synthesized cholesterol, oleic acid incorporation into cholesteryl ester was not increased. We conclude that 25-hydroxycholesterol increases intestinal ACAT activity. The effect of 25-hydroxycholesterol on ACAT is dependent upon the availability of cholesterol to the enzyme. At cholesterol concentrations below saturation, the oxygenated sterol has a stimulatory effect. If ACAT is saturated, 25-hydroxycholesterol has no effect. ACAT catalyzes the esterification of two separate pools of cholesterol within the enterocyte, i.e., newly synthesized cholesterol and membrane cholesterol. 25-Hydroxycholesterol increases the esterification rate of cholesterol in both pools.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				S. N. Mathur, K. R. Watt, and F. J. Field Regulation of intestinal NPC1L1 expression by dietary fish oil and docosahexaenoic acid J. Lipid Res., February 1, 2007; 48(2): 395 - 404. [Abstract] [Full Text] [PDF]

				X. Du, Y. H. Pham, and A. J. Brown Effects of 25-Hydroxycholesterol on Cholesterol Esterification and Sterol Regulatory Element-binding Protein Processing Are Dissociable: IMPLICATIONS FOR CHOLESTEROL MOVEMENT TO THE REGULATORY POOL IN THE ENDOPLASMIC RETICULUM J. Biol. Chem., November 5, 2004; 279(45): 47010 - 47016. [Abstract] [Full Text] [PDF]

				G. J. Schroepfer Jr. Oxysterols: Modulators of Cholesterol Metabolism and Other Processes Physiol Rev, January 1, 2000; 80(1): 361 - 554. [Abstract] [Full Text] [PDF]